Systems and techniques for restoring and maintaining intervertebral anatomy

ABSTRACT

Techniques and systems for distracting a spinal disc space and supporting adjacent vertebrae are provided. Trial instruments are insertable into the disc space to determine a desired disc space height and to select a corresponding implant. Implants can be also be self-distracting and the implant providing the desired disc space height can be implanted in the spinal disc space.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 15/652,662, filed Jul. 18, 2017; which is a continuation of U.S.patent application Ser. No. 14/590,471, filed Jan. 6, 2015 (U.S. Pat.No. 9,737,415); which is a continuation of U.S. patent application Ser.No. 13/689,910, filed Nov. 30, 2012 (U.S. Pat. No. 9,011,541); which isa divisional of U.S. patent application Ser. No. 11/451,836, filed Jun.13, 2006 (U.S. Pat. No. 8,349,011); which is a divisional of U.S. patentapplication Ser. No. 10/274,856 filed on Oct. 21, 2002 (U.S. Pat. No.7,063,725); all of which are incorporated herein by reference in theirentirety.

BACKGROUND

Various surgical instruments and methods have been devised for theimplantation of devices into the disc space between adjacent vertebraeof the spinal column. For example, spinal fusion procedures can requiresequential distraction to restore the disc space height prior toinserting a pair of fusion devices in the disc space in side-by-siderelation. To implant these devices, an initial opening or openings aremade in the disc space at the locations through which the devices are tobe inserted. A first distractor is inserted in the disc space at one ofthe device locations. A second larger distractor is inserted in the discspace at the other of the device locations. Sequential distraction inalternate disc space locations is continued until the desired disc spaceheight is achieved. The next to last inserted distractor is thenremoved. The disc space is prepared for insertion of one fusion devicein the location previously occupied by the withdrawn distractor whilethe other distractor maintains the restored disc space height.

In another technique, a spinal disc space is accessed and distracted forinsertion of an implant. Distraction of the disc space is maintained byapplying a distraction force to bone screws engaged in the vertebrae oneach side of the disc space.

While the above procedure can be effective for some techniques, thereare disadvantages. For example, dissection and retraction of tissue,vasculature and nervature is required to accommodate the pair ofdistractors inserted in the disc space, or to accommodate the externaldistractors. Alternating sequential distraction can be time-consumingand requires many steps to complete the surgical procedure. Engagementof bone screws to the vertebrae and application of a distraction forceto the engaged bone screws also requires additional time and steps inthe surgical procedure.

There remains a need for instruments and techniques for restoring andmaintaining a spinal disc space anatomy that minimizes dissection andretraction and of tissue, vasculature and nervature. There furtherremains a need for instruments and techniques for restoring andmaintaining a spinal disc space anatomy that minimizes the steps andcomplexity of the procedure during surgery.

SUMMARY

Implants are provided that can be sequentially inserted and withdrawnfrom a spinal disc space to restore the disc space to a desired discspace height and to post-operatively maintain the desired spinal discspace height when a selected implant is left in the spinal disc space.

Instruments are provided for determining the desired disc space heightand for selecting an implant providing the desired disc space heightwhen inserted in the collapsed disc space.

Implants are provided that can have the same height and leading endportion configuration of at least some trial instruments of a set oftrial instruments. Each trial instrument of the set has a trial bodyproviding a restored disc space height and a leading end portionconfigured to distract the disc space to the restored disc space height.

Implants are provided that have a self-distracting lead endconfiguration.

Methods for restoring and maintaining a spinal disc space height areprovided that include, for example, sequentially inserting andwithdrawing a number of implants into a collapsed, non-distracted spinaldisc space. The implant providing a desired disc space height is left inthe disc space to post-operatively maintain the desired disc spaceheight.

Methods for restoring and maintaining a spinal disc space height areprovided that include, for example, sequentially inserting andwithdrawing a number of trial bodies into a collapsed spinal disc space.When an inserted trial body is withdrawn, the non-distracted disc spaceat least partially collapses. Each of the inserted trial bodies has aleading end portion configured to re-distract the disc space afterwithdrawal of the previous trial body. An inserted trial body isdetermined to provide a desired disc space height. An implantcorresponding in height and leading end portion configuration to thetrial body providing the desired disc space height can be inserted intothe disc space to restore the collapsed disc space to the desired discspace height and post-operatively maintain the desired disc spaceheight.

Related objects, advantages, aspects, forms, and features of the presentinvention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are elevation views of a self-distracting trialinstrument and a pair of adjacent vertebrae before and after insertionof the trial instrument.

FIGS. 2A and 2B are elevation views of a self-distracting implant and apair of vertebrae before and after insertion of the implant.

FIGS. 3A and 3B are elevation views of a distal portion of anotherembodiment self-distracting trial instrument and a pair of adjacentvertebrae before and after insertion of the trial instrument.

FIGS. 4A and 4B are elevation views of another embodimentself-distracting implant and a pair of adjacent vertebrae before andafter insertion of the implant.

FIG. 5 shows a set of trial instruments.

FIG. 6 shows a set of implants and implant insertion instruments.

FIG. 7 is a perspective view of another embodiment implant and implantinsertion instrument.

FIG. 8 is a perspective view of an embodiment of the implant of FIG. 7.

FIG. 9 is an exploded perspective view of the implant of FIG. 8.

FIG. 10A is an elevation view of a proximal end of the implant of FIG. 7coupled to the insertion instrument.

FIG. 10B is an elevation view of the proximal end of the implant of FIG.7 uncoupled from the insertion instrument.

FIGS. 11A and 11B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 12A and 12B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 13A and 13B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 14A and 14B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 15A and 15B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 16A and 16B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 17A and 17B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 18A and 18B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 19A and 19B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 20A and 20B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 21A and 21B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 22A and 22B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 23A and 23B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 24A and 24B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 25A and 25B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 26A and 26B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 27A and 27B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 28A and 28B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

FIGS. 29A and 29B are a plan view and side view, respectively, of adistal portion of another embodiment trial instrument.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any such alterations and furthermodifications in the illustrated device, and any such furtherapplications of the principles of the invention as illustrated thereinbeing contemplated as would normally occur to one skilled in the art towhich the invention relates.

Methods, techniques, instrumentation and implants are provided torestore and/or maintain a collapsed spinal disc space at a desired discspace height. The instruments and implants may be used in techniquesemploying minimally invasive instruments and technology to access thedisc space. Access to the collapsed disc space can be uni-portal,bi-portal, or multi-portal. The instruments and implants may also beemployed in open surgical procedures in which skin and tissue isdissected and retracted to access the collapsed spinal disc space. Themethods, techniques, instruments and implants may also be employed inany surgical approach to the spine, including lateral, antero-lateral,postero-lateral, posterior, and anterior approaches. Also, the surgicalmethods, techniques, instruments and implants may find application atall vertebral segments of the spine, including the lumbar, thoracic andcervical spinal regions.

Referring now to FIG. 1A, there is shown an implant trial instrument 20having a proximal handle 22, a shaft 24 extending distally from handle22, and a trial body 26. Trial body 26 includes a proximal end 28connected with or formed with a distal end of shaft 24 and a leadinginsertion end 30. Trial body 26 further includes an upper surface 26 aand an opposite lower surface 26 b. Trial body has a height H1 betweenupper surface 26 a and lower surface 26 b. Proximal end 28 can betapered or otherwise configured to provide a gradual transition betweensurfaces 26 a, 26 b to facilitate withdrawal of trial body 26 from thespinal disc space.

Trial instrument 20 is insertable into a collapsed disc space D betweenadjacent vertebrae V1 and V2. Leading end portion 30 can be providedwith a rounded nose-like shape that allows at least a portion of leadingend portion 30 to be inserted into a collapsed, undistracted disc spaceD. As trial body 26 is advanced into disc space D, the edges ofvertebrae V1 and V2 ride upwardly and downwardly, respectively, alongthe rounded nose portion of leading end portion 30. Once leading endportion 30 is completely inserted, collapsed disc space D is distractedto restore disc space D′, as shown in FIG. 1B. Restored disc space D′has a height between the endplates of the adjacent vertebrae V1, V2which corresponds to height H1 of trial body 26 between upper surface 26a and lower surface 26 b.

With trial body 26 inserted in disc space D, the surgeon can determinewhether disc space D has been adequately distracted or positioned to adesired disc space height by the tactile feel and visual inspection oftrial instrument 20 in the disc space. For example, if trial instrument20 is easily moved, or does not provide a snug fit, then a trialinstrument 20 may be withdrawn and a second trial instrument having atrial body with a greater height H1 is inserted. Alternatively, if thefit of trial body 26 is too tight or won't fit, it can be withdrawn andanother trial instrument having a trial body with a smaller height H1can be inserted in disc space D. The particular trial instrument 20providing a restored disc space height that corresponds to a desireddisc space height is noted by the surgeon for selection of an implant.

In FIG. 2A there is shown an implant 40 having a body 42. Body 42includes a proximal end 44 and a leading insertion end 46. Body 42further includes an upper surface 42 a and an opposite lower surface 42b. Body 42 has a height H1 between surfaces 42 a, 42 b. Leadinginsertion end 46 is the same size and shape as leading end portion 30 oftrial body 26. Height H1 between surfaces 42 a, 42 b of implant body 42is also the same of height H1 between surfaces 26 a, 26 b of trial body26.

In use, implant 40 can be selected from a set of implants correspondingin size and shape with a set of trial instrument bodies 26. The selectedimplant corresponds in size and shape with the trial body 26 providingthe desired fit and desired disc space height for collapsed disc spaceD. Once implant 40 is selected, trial body 26 is withdrawn from restoreddisc space D′, and restored disc space D′ at least partially collapses.Implant 40 has a leading end portion 46 that is the same size and shapeas that of trial body 26, and implant 40 will be insertable into thecollapsed disc space D since trial body 26 was insertable in collapseddisc space D. Implant 40 restores and post-operatively maintains thecollapsed disc space D at a desired disc space height H1 betweenvertebrae V1 and V2, as shown in FIG. 2B.

Referring to FIG. 3A, an alternate embodiment trial instrument 20′ isshown. Trial instrument 20′ can include a proximal handle (not shown), ashaft 24 extending distally from the handle, and a trial body 26′. Trialbody 26′ includes a proximal end 28′ connected with or formed with adistal end of shaft 24′ and a leading insertion end 30′. Trial body 26′further includes an upper surface 26 a′ and an opposite lower surface 26b′. Trial body has a height H1 between upper surface 26 a′ and lowersurface 26 b′. Proximal end 28′ can be tapered or otherwise configuredto provide a gradual transition between surfaces 26 a′, 26 b′ tofacilitate withdrawal of trial body 26′ from the spinal disc space.

Trial instrument 20′ is insertable into a collapsed disc space D betweenadjacent vertebrae V1 and V2. Leading end portion 30′ can be providedwith an aggressively tapered nose portion as compared to leading endportion 30, which is overlaid on leading end portion 30′ in FIG. 3A forcomparison. Leading end portion 30′ can have a pointed or blunt end noseportion 30 a′. Nose portion 30 a′ can be relatively small in height forinsertion into a severely collapsed disc space D.

For example, the height of nose portion 30 a′ can be in the range from 3millimeters or less to about 5 or 6 millimeters. Leading end portion 30′further includes an upper transition surface 30 b′ and a lowertransition surface 30 c′. Transition surfaces 30 b′, 30 c′ extend fromnose portion 30 a′ to respective ones of the upper surface 26 a′ andlower surface 26 b′. Transition surfaces 30 b′, 30 c′ provide a smoothand gradual transition for separation of collapsed vertebrae V1 and V2as trial body 26′ is advanced into collapsed disc space D. As shown inFIG. 3B, once leading end portion 30′ is completely inserted, collapseddisc space D is distracted or restored by body 26′. Vertebrae V1′ andV2′ can be separated by height H1 to provide restored disc space D′having a height between the endplates of the adjacent vertebrae whichcorresponds to height H1 of trial body 26′ between upper surface 26 a′and lower surface 26 b′.

In FIG. 4A there is shown an implant 40′ having a body 42′. Body 42′includes a proximal end 44′ and a leading insertion end 46′. Body 42′further includes an upper surface 42 a′ and an opposite lower surface 42b′. Body 42′ has a height H1 between surfaces 42 a′, 42 b′. Leadinginsertion end 46′ is the same size and shape as leading end portion 30′of trial body 26′. Height H1 between surfaces 42 a′, 42 b′ of implantbody 42′ has height H1 between surfaces 26 a′, 26 b′ of trial body 26′.

Leading end portion 46′ can be provided with an aggressively taperednose portion such as that provided with leading end portion 30′ of trialinstrument 20′. Leading end portion 46′ can have a pointed or blunt noseportion 46 a′. Nose portion 46 a′ can be relatively small in height forinsertion into a severely collapsed disc space D. For example, theheight of nose portion 46 a′ can range from 3 millimeters or less toabout 5 to 6 millimeters. Leading end portion 46′ further includes anupper transition surface 46 b′ and a lower transition surface 46 c′.Transition surfaces 46 b′, 46 c′ extend from nose portion 46 a′ torespective ones of the upper surface 42 a′ and lower surface 42 b′.Transition surfaces 46 b′, 46 c′ provide a smooth and gradual transitionfor separation of collapsed vertebrae V1 and V2 as implant body 42′ isadvanced into collapsed disc space D. Leading end portion 46′ iscompletely inserted to restore collapsed disc space D. As shown in FIG.4B, the distracted or restored disc space D′ between vertebrae V1′ andV2′ has a height between the endplates of the adjacent vertebrae V1′,V2′ which corresponds to the height H1 of implant body 42′ between uppersurface 42 a′ and lower surface 42 b′.

In use, implant 40′ can be selected from a set of implants havingsimilar configurations but different heights H1. Implant 40′ can beselected to correspond in height with the trial body 26′ providing thedesired fit and desired disc space height for collapsed disc space D.Once implant 40′ is selected, the last inserted trial body 26′ iswithdrawn from restored disc space D′, and restored disc space D′collapses. However, since leading end portion 46′ of implant 40′ is thesame as that of leading end portion 30′ of trial body 26′, and the lastinserted trial body 26′ was insertable in the collapsed disc space D,the selected implant 40′ will also be insertable in the collapsed discspace D. Implant 40′ thus provides a restored disc space D′corresponding to the desired disc space height indicated by trial body26′, and the selected and inserted implant 40′ post-operativelymaintains the restored disc space D′ at a desired disc space height H1.

In the embodiments of FIGS. 1A-4B, it is contemplated that implants 40,40′ could be releasably attachable to the distal end of shaft 24 forinsertion into collapsed disc space D. It is further contemplated that,rather than providing separate trial instruments, a series of implants40, 40′ could be provided of increasing height H1. The surgeon couldinsert and, if necessary, withdraw various ones of the implants 40, 40′to determine which of the various height implants provide a desired discspace height. The implant providing the desired disc space height can beleft in the disc space to post-operatively maintain the desired discspace height. The number of steps in the surgical procedure and timerequired for surgery can be further reduced by providing suchself-distracting implants that do not require pre-distraction of thecollapsed disc space for insertion. However, providing trial instrumentscan be advantageous for implants made from some types of bone materialor other material that may not withstand impaction into a collapsed discspace since the trial instruments provide an indication that the implantwill fit before it is impacted into the disc space, reducing the chanceof damaging the implant during withdrawal or during insertion.

It is further contemplated that implants 40′ can be provided in a set ofimplants having increasing heights H1. The height at leading end portion46′ can be the same for each implant 40′ of the set so that any of theimplants of the set could be selected for insertion into the collapseddisc space when it is initially accessed. Sequential distraction withthe implants 40′ may not be needed or can be minimized if one of thefirst selected implants provides the desired disc space height and fit.For example, each of the various height implants 40′ of the set caninclude transition surfaces 46 b′, 46 c′ that taper from the same heightnose portion 46 a′ provided on each implant to the differing heights H1between upper and lower surfaces 42 a′, 42 b′ provided on each implant.

In FIG. 5 there is shown a trial instrument set 50 having a number oftrial instruments 52, 54, 56, 58, 60, 62, 64, 66, 68 and 70. Trialinstrument 52 includes a handle 52 a, a shaft 52 b extending distallyfrom handle 52 a, and a trial body 52 c. Each of the other trialinstruments also includes a handle, a shaft and a trial body. It iscontemplated that each trial body of the trial instruments provides adifferent height between an upper and a lower contact surface thereoffor restoring a collapsed disc space. For example, trial instrument 52can be provided with a trial body having the smallest height H of theinstrument set 50, and trial instrument 70 can be provided with a trialbody having the largest height H′ of the instrument set 50. Theremaining trial instruments can provide a number of different heighttrial instruments ranging in height between H and H′. In one particularembodiment of instrument set 50, the height of the trial instruments inthe set increase in one millimeter increments. In another particularembodiment, the heights range from 6 millimeters to 15 millimeters inone millimeter increments. Other increments and other ranges of heightsare also contemplated.

In FIG. 6 there is shown a set 80 of implant insertion instruments 82,84, 86. Implant insertion instrument 82 includes a handle 82 a, a shaft82 b, and an implant 82 c releasably coupled to the distal end of shaft82 b. Implant 82 c can have a height H″′ between its upper and lowervertebral contacting surfaces. Implant insertion instrument 84 includesa handle 84 a, a shaft 84 b, and an implant 84 c releasably coupled tothe distal end of shaft 84 b. Implant 84 c can have a height H″ betweenits upper and lower vertebral contacting surfaces. Implant insertioninstrument 86 includes a handle 86 a, a shaft 86 b, and an implant 86 creleasably coupled to the distal end of shaft 86 b. Implant 86 c canhave a height H′ between its upper and lower vertebral contactingsurfaces. As further shown in FIG. 6, each of the implants 82 c, 84 c,86 c is releasable from its insertion instrument so that any one ofimplants 82 c, 84 c, 86 c can be selected for insertion andpost-operative implantation in the disc space.

It is contemplated that implant insertion instrument set 80 can beprovided with trial instrument set 50. Each of the implants can bepreloaded on an instrument shaft to save time during surgery. However,each of the implants could also be provided separated with a singleinstrument shaft and then, when the desired implant height isdetermined, the appropriate implant coupled to the instrument shaft.Heights H′″, H″, and H′ of implants 82 c, 84 c, 86 c correspond to theheights H″′, H″, H′ of the trial bodies of trial instruments 66, 68, and70, respectively. Accordingly, the surgeon determines which of the trialbodies of trial instruments 66, 68 or 70 has a height providing thedesired fit in the disc space by alternately inserting selected ones ofthe trial bodies in the disc space. The trial body providing the desireddisc space height is removed and the implant insertion instrumentproviding an implant with the same height is selected, and the implantis inserted into the disc space to restore and maintain the desired discspace height.

It is contemplated that more than three implant insertion instruments82, 84, 86 could be provided with implant insertion instrument set 80.For example, a set of implant insertion instruments could be providedwith implants each having a height corresponding to the height of one ofthe trial bodies of trial instrument set 50. It is further contemplatedthat, rather than providing any trial instrument set 50, an implantinsertion instrument set 80 can be provided with a number of implantsproviding the desired range of heights. The implants of the implantinsertion instrument set are sequentially inserted and, if necessary,withdrawn from the collapsed disc space. The implant providing thedesired fit and desired disc space height is left in the disc space topost-operatively maintain the disc space height.

In FIG. 7 there is shown an implant 110 coupled to the distal end of aninsertion instrument 90. Insertion instrument 90 includes a proximalshaft 92 and a proximal end cap 94. An intermediate hub 96 is located atthe distal end of proximal shaft 92. A slap hammer or other instrumentfor assisting in impacting implant 110 into a disc space can be securedabout proximal shaft 92 and impacted against end cap 94 and/or hub 96.

Extending distally from hub 96 is an actuator assembly including a firstmember 98 and a second member 100. First member 98 includes a couplingportion 108 at its distal end, and second member 100 includes a couplingportion 104 at its distal end. First and second members 98, 100 arepivotally coupled at pin 106 so that at least one of the couplingportions 104, 108 is movable relative to the other coupling portionabout pin 106. In the illustrated embodiment, coupling portion 104 ismovable about pin 106 in the directions of arrow P1 by moving handle 102in the directions of arrows P2 to engage and release implant 110 betweencoupling members 104, 108.

In one embodiment, implant 110 is comprised of two or more pieces ofmaterial that can be temporarily or permanently joined together, and canbe held together by insertion instrument 90 during insertion into thedisc space. Implant 110 includes a self-distracting leading end portion116 to facilitate insertion in a collapsed disc space. In anotherembodiment, implant 110 is comprised of a single piece of material. Thematerial comprising implant 110 can be solid, porous, multiply drilled,perforated, open and/or spongy, for example.

Further details regarding one embodiment of implant 110 are shown inFIG. 8. Implant 110 includes a body 112 with an upper surface 114 and anopposite lower surface 117. The upper and lower surfaces 114, 117 can beprovided with grooves, recesses, ridges, serrations, knurlings, spikes,roughened surfaces, or smooth surfaces for engaging the endplates of theadjacent vertebrae. Body 112 includes a leading end portion 116 that isrounded or tapered configured so that body 112 distracts the adjacentvertebrae as it is inserted in a collapsed disc space. Body 112 alsoincludes a proximal end wall 111, and sidewalls 113, 115 extendingbetween proximal end wall 111 and leading end portion 116. As shown inFIGS. 10A and 10B, a first notch 124 a in lateral wall 113 and a secondnotch 124 b in lateral wall 115 each extend distally from and open atproximal end wall 111. First notch 124 a can be provided with an indent126 a therein, and second notch 124 can be provided with an indent 126 btherein.

In FIG. 9, implant 112 is shown in an exploded view. Body 112 can beprovided in a first lateral section 112 a and a second lateral section112 b. Lateral sections 112 a, 112 b each include a correspondingportion of the upper surface 114 a, 114 b, the lower surface, andleading end portion 116 a, 116 b. One of the lateral sections, such aslateral section 112 a, can be provided with a bore 120, and the other ofthe lateral sections, such as lateral section 112 b can be provided witha pin 118. Pin 118 is insertable into bore 120 to secure lateralsections 112 a, 112 b to one another. Lateral section 112 a includes amedial surface 122 a and lateral section 112 b includes a medial surface122 b. Medial surfaces 122 a, 122 b are positioned adjacent one anotherwhen lateral sections 112 a, 122 b are assembled. Medial surfaces 122 a,122 b can each be provided with peaks and valleys that interdigitatewith peaks and valleys of the other medial surface to assist in holdinglateral sections 112 a, 112 b together and prevent relative movementthere between. In the illustrated embodiment, the peaks and valleysextend in the direction between upper surface 114 and lower surface 117.Other orientations for the peaks and valleys are also contemplated, suchas extending between leading end portion 116 and proximal end 111, orextending diagonally.

In the embodiment of implant 110 discussed above, it is contemplatedthat implant 110 can be made of cortical bone cut so that thelongitudinal axes of lateral sections 112 a, 112 b between leading endportions 116 a, 116 b and proximal end 111 are parallel to thelongitudinal axis of the host bone from which the sections are cut. Bycutting through the host bone longitudinally to obtain the implantsections, leading end portion 116 of implant 110 is provided withmaximum strength and durability to withstand impaction of implant 110into the disc space. Other embodiments of implant 110 contemplate thatimplant 110 is provided as an integral unit, and can be made from asingle piece of bone material, or made from non-bone material.

As shown in FIGS. 10A and 10B, the coupling portions 104, 108 arepositionable in notches 124 a, 124 b to engage implant 110 to insertioninstrument 90. Coupling portion 104 can include a protrusion 105positionable in detent 126 b, and coupling portion 108 can include aprotrusion 109 positionable in detent 126 a. In FIG. 10A, couplingportions 104, 108 define a width W2 between the lateral outside edgesthereof that is less than a width W1 between lateral walls 113, 115 ofimplant 110. Thus, coupling portions 104, 108 and insertion instrument90 do not protrude laterally from implant 110 during insertion. As shownin FIG. 10B, coupling portions 104, 108 are moved away from one anotherto disengage implant 110 and to remove protrusions 105, 109 from detents126 b, 126 a, respectively so that insertion instrument 90 can belongitudinally withdrawn from implant 110. The width between the lateraloutside edges of coupling members 104, 108 can be limited in theuncoupled position to be the same as or less than width W1 of implant110. In this manner, insertion instrument 90 can be uncoupled fromimplant 110 while maintaining a low profile that does not protrude orproject laterally beyond lateral walls 113, 115. As a result, thepathway through which implant 110 is positioned to the collapsed discspace need only be large enough to accommodate implant 110.

Referring now to FIGS. 11A-11B, there is shown an embodiment of a distalportion 140 of a trial instrument attachable to an insertion instrument.Other embodiment distal portions 140 for trial instruments are shownFIGS. 12A-20B that are similar to the distal portion of FIG. 11A butwith differing geometrical properties for determining a desired discspace height. However, as discussed further below, the distal portionsof FIGS. 12A-20B have geometrical properties which differ from distalportion 140, providing a set of distal portions 140 which can besequentially inserted and withdrawn from a collapsed spinal disc spaceto determine an appropriate implant for insertion therein. In addition,it is contemplated that implants could be provided having the same sizeand shape of each of the trial bodies of distal portions 140 shown inFIGS. 11A-20B.

Distal portion 140 includes a trial body 142 and a shaft couplingportion 144 extending proximally from trial body 142. Shaft couplingportion 144 can be coupled to an insertion instrument. Other embodimentscontemplate that trial body 142 can be integral with the insertioninstrument. Contemplated coupling arrangements between trial body 142and the insertion instrument include clamping connections, frictionalconnections, set screw connections, threaded connections, bayonetconnections, and ball-detent connections, for example. Trial body 142includes an upper surface 142 a and a lower surface 142 b for contactingthe endplate of the adjacent vertebra. Trial body 142 also includeslateral surfaces 142 c and 142 d. Rounded or tapered lateral transitionsurfaces extend between upper and lower surfaces 142 a, 142 b and therespective lateral surfaces 142 c, 142 d. Trial body 142 furtherincludes a leading end portion 146 and a proximal end 148. Proximal end148 can be tapered to facilitate withdrawal of trial body 142 from thedisc space. Leading end portion 146 includes a nose portion 146 a androunded portions transitioning to the upper and lower surfaces 142 a,142 b.

Distal portion 140 includes an overall length L1, and trial body 142includes a length L2. Upper and lower surfaces 142 a, 142 b can becurved along a radius R2 to generally mate with the vertebral endplategeometry. The upper and lower transition surfaces of leading end portion146 can be curved along radius R2′. Trial body 142 includes an overallmaximum height H2 between upper and lower surfaces 142 a, 142 b. Upperand lower surfaces 142 a, 142 b can be curved to provide a height H2′ atleading end 146. Height H2′ is less than height H2 to facilitateinsertion of leading end portion 146 into the spinal disc space. Trialbody 142 can be provided with an overall width W3 between lateralsurfaces 142 c and 142 d.

In FIGS. 12A and 12B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R3. Theupper and lower transition surfaces of leading end portion 146 arecurved along radius R3′. Trial body 142 has an overall maximum height H3between upper and lower surfaces 142 a, 142 b. Upper and lower surfaces142 a, 142 b are curved to provide a height H3′ at leading end portion146. Height H3′ is less than height H3 to facilitate insertion ofleading end portion 146 into the spinal disc space.

In FIGS. 13A and 13B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R4. Theupper and lower transition surfaces of leading end portion 146 arecurved along radius R4′. Trial body 142 has an overall maximum height H4between upper and lower surfaces 142 a, 142 b. Upper and lower surfaces142 a, 142 b are curved to provide a height H4′ at leading end portion146. Height H4′ is less than height H4 to facilitate insertion ofleading end portion 146 into the spinal disc space.

In FIGS. 14A and 14B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R5. Theupper and lower transition surfaces of leading end portion 146 arecurved along radius R5′. Trial body 142 has an overall maximum height H5between upper and lower surfaces 142 a, 142 b. Upper and lower surfaces142 a, 142 b are curved to provide a height H5′ at leading end portion146. Height H5′ is less than height H5 to facilitate insertion ofleading end portion 146 into the spinal disc space.

In FIGS. 15A and 15B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R6. Theupper and lower transition surfaces of leading end portion 146 arecurved along radius R6′. Trial body 142 has an overall maximum height H6between upper and lower surfaces 142 a, 142 b. Upper and lower surfaces142 a, 142 b are curved to provide a height H6′ at leading end portion146. Height 116′ is less than height H6 to facilitate insertion ofleading end portion 146 into the spinal disc space.

In FIGS. 16A and 16B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R7. Theupper and lower transition surfaces of leading end portion 146 arecurved along radius R7′. Trial body 142 has an overall maximum height H7between upper and lower surfaces 142 a, 142 b. Upper and lower surfaces142 a, 142 b are curved to provide a height H7′ at leading end portion146. Height H7′ is less than height H7 to facilitate insertion ofleading end portion 146 into the spinal disc space.

In FIGS. 17A and 17B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R8. Theupper and lower transition surfaces of leading end portion 146 arecurved along radius R8′. Trial body 142 has an overall maximum height H8between upper and lower surfaces 142 a, 142 b. Upper and lower surfaces142 a, 142 b are curved to provide a height 118′ at leading end portion146. Height 118′ is less than height H8 to facilitate insertion ofleading end portion 146 into the spinal disc space. Upper and lowersurfaces 142 a, 142 b further taper along proximal end 148 to form angleα with the central axis of the insertion instrument. Angle α provides asmooth transition between coupling portion 144 and body 142 to preventbody 142 from hanging up or catching on the vertebral endplates as it iswithdrawn.

In FIGS. 18A and 18B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R9. Theupper and lower transition surfaces of leading end portion 146 arecurved along radius R9′. Trial body 142 has an overall maximum height H9between upper and lower surfaces 142 a, 142 b. Upper and lower surfaces142 a, 142 b are curved to provide a height H9′ at leading end portion146. Height H9′ is less than height H9 to facilitate insertion ofleading end portion 146 into the spinal disc space. Upper and lowersurfaces 142 a, 142 b further taper along proximal end 148 to form angleα with the central axis of the insertion instrument.

In FIGS. 19A and 19B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R10.The upper and lower transition surfaces of leading end portion 146 arecurved along radius R10′. Trial body 142 has an overall maximum heightH10 between upper and lower surfaces 142 a, 142 b. Upper and lowersurfaces 142 a, 142 b are curved to provide a height H10′ at leading endportion 146. Height H10′ is less than height H10 to facilitate insertionof leading end portion 146 into the spinal disc space. Upper and lowersurfaces 142 a, 142 b further taper along proximal end 148 to form angleα with the central axis of the insertion instrument.

In FIGS. 20A and 20B, distal portion 140 is provided with a body 142having upper and lower surfaces 142 a, 142 b curved along radius R11.The upper and lower transition surfaces of leading end portion 146 arecurved along radius R11′. Trial body 142 has an overall maximum heightH11 between upper and lower surfaces 142 a, 142 b. Upper and lowersurfaces 142 a, 142 b are curved to provide a height H11′ at leading endportion 146. Height H11′ is less than height H11 to facilitate insertionof leading end portion 146 into the spinal disc space. Upper and lowersurfaces 142 a, 142 b further taper along proximal end 148 to form angleα with the central axis of the insertion instrument.

It is contemplated that a set of self-distracting implants could beprovided by modifying each of the distal portions 140 of FIGS. 11A-20Bso that between its distal and proximal ends the implant has a lengththat fits within a spinal disc space. For example, shaft couplingportion 144 could be removed, or trial body 142 could be truncated at aproximal end wall 150. The proximal end of the implant could includes athreaded hole in the proximal end wall, notches in the lateral walls, orother suitable configuration for releasable engagement with an insertioninstrument.

In one specific embodiment of a trial instrument set employing thedistal portions of FIGS. 11A-20B, each of the bodies 142 can be providedwith a width W3 of about 10 millimeters and a length L1 of about 42millimeters. Each of the distal portions 140 can be provided with anoverall length L2 of about 60 millimeters. Leading end portion 146 canbe provided with a radius R of 5 millimeters between lateral surfaces142 c, 142 d, and angle α can be about 25 degrees.

In the specific embodiment, height H2 of the FIG. 11A embodiment is 6millimeters. Each of the heights H3 through H11 can increase in onemillimeter increments from height H2 to height H11. Thus, height H11 is15 millimeters. Furthermore, the reduced height at each of the leadingend portions, such as height H2′ can be 4 millimeters, or 2 millimetersless than height H2. Similarly, each of the heights H3′ through H11′ canbe 2 millimeters less than the corresponding heights H3 through H11. Theradii R2′ through R5′ transitioning between the nose portion 146 a andupper and lower surfaces 142 a, 142 b can each be 2 millimeters. RadiiR6′ and R7′ can each be 3 millimeters, and radii R8′ through R11′ caneach be 4 millimeters.

The specific embodiment further contemplates that upper and lowersurface 142 a, 142 b have a different curvature for each of the bodies142 to conform to an adjacent vertebral endplate associated with theparticular distraction height provided by the particular body 142. Forexample, radius R2 can about 221 millimeters, radius R3 can be about 179millimeters, radius R4 can be about 152 millimeters, radius R5 can beabout 133 millimeters, radius R6 can be about 119 millimeters, radius R7can be about 108 millimeters, radius R8 can be about 100 millimeters,radius R9 can be about 92 millimeters, radius R10 can be about 86millimeters, and radius R11 can be about 81 millimeters.

While specific dimensional and geometrical features have been providedfor one particular embodiment of a set of distal portions 140, it shouldbe understood however, that such dimensional and geometrical attributesare provided for a specific embodiment, and other embodimentscontemplate other dimensions than those provided herein.

Referring now to FIGS. 21A-21B, there is shown an embodiment of a distalportion 240 of a trial instrument attachable to an insertion instrument.Other embodiment distal portions 240 for trial instruments are shownFIGS. 22A-29B that are similar to the distal portion of FIG. 21A butwith differing geometric properties for determining a desired disc spaceheight. However, as discussed further below, the distal portions ofFIGS. 22A-29B have geometrical properties which differ from the distalportion 240, providing a set of distal portions 240 which can besequentially inserted and withdrawn from a collapsed spinal disc spaceto determine an appropriate implant for insertion therein. In addition,it is contemplated that implants could be provided having the same sizeand shape of each of the trial bodies of the distal portions 240 shownin FIGS. 21A-29B.

Distal portion 240 includes a trial body 242 and a shaft couplingportion 244 extending proximally therefrom. Shaft coupling portion 244can be coupled to an insertion instrument. Other embodiments contemplatethat trial body 242 can be integral with the insertion instrument.Contemplated coupling arrangements between trial body 242 and theinsertion instrument include clamping connections, frictionalconnections, set screw connections, threaded connections, bayonetconnections, and ball-detent connections, for example. Trial body 242includes an upper surface 242 a and a lower surface 242 b for contactingthe endplate of the adjacent vertebra. Trial body 242 also includeslateral surfaces 242 c and 242 d. Rounded or tapered lateral transitionsurfaces extend between upper and lower surfaces 242 a, 242 b and therespective lateral surfaces 242 c, 242 d. Trial body 242 furtherincludes a leading end portion 246 and a proximal end 248. Proximal end248 can tapered to facilitate withdrawal of trial body 242 from the discspace. Leading end portion 246 includes a flat or slightly rounded noseportion 246 a and upper and lower transition surfaces 246 b, 246 cextending therefrom. Upper and lower transition surfaces 246 b, 246 cprovide a gradually increasing distraction height extending from noseportion 246 a to facilitate distraction of the adjacent vertebrae.

Distal portion 240 includes an overall length L1, and trial body 242includes a length L2. Upper and lower surfaces 242 a, 242 b can becurved along a radius R3 to generally mate with the vertebral endplategeometry. The upper and lower transition surfaces 246 b, 246 c ofleading end portion 246 can be tapered along angle A1 relative to acentral axis extending longitudinally through body 242. Trial body 242includes an overall maximum height H3 between upper and lower surfaces242 a, 242 b. Upper and lower surfaces 242 a, 242 b are tapered fromheight H3 to height H12 at nose portion 246 a. A radius R12 can providea smooth transition between transition surfaces 246 b, 246 c and noseportion 246 a. Height H12 is less than height H3 to facilitate insertionof leading end portion 246 into the spinal disc space. Trial body 242can be provided with an overall width W3 between lateral surfaces 242 cand 242 d.

In FIGS. 22A and 22B, distal portion 240 is provided with a body 242having upper and lower surfaces 242 a, 242 b curved along radius R4. Theupper and lower transition surfaces 246 b, 246 c of leading end portion246 can be tapered along angle A1 relative to central axis C extendinglongitudinally through body 242. Trial body 242 includes an overallmaximum height H4 between upper and lower surfaces 242 a, 242 b. Upperand lower surfaces 242 a, 242 b are tapered from height H4 to height H12at nose portion 246 a. Radius R12 can provide a smooth transitionbetween transition surfaces 246 b, 246 c and nose portion 246 a. HeightH12 is less than height H4 to facilitate insertion of leading endportion 246 into the spinal disc space.

In FIGS. 23A and 23B, distal portion 240 is provided with a body 242having upper and lower surfaces 242 a, 242 b curved along radius R5. Theupper and lower transition surfaces 246 b, 246 c of leading end portion246 can be tapered along angle A2 relative to central axis C extendinglongitudinally through body 242. Trial body 242 includes an overallmaximum height H5 between upper and lower surfaces 242 a, 242 b. Upperand lower surfaces 242 a, 242 b are tapered from height H5 to height H12at nose portion 246 a. Radius R12 can provide a smooth transitionbetween transition surfaces 246 b, 246 c and nose portion 246 a. HeightH12 is less than height H5 to facilitate insertion of leading endportion 246 into the spinal disc space.

In FIGS. 24A and 24B, distal portion 240 is provided with a body 242having upper and lower surfaces 242 a, 242 b curved along radius R6. Theupper and lower transition surfaces 246 b, 246 c of leading end portion246 can be tapered along angle A2 relative to central axis C extendinglongitudinally through body 242. Trial body 242 includes an overallmaximum height H6 between upper and lower surfaces 242 a, 242 b. Upperand lower surfaces 242 a, 242 b are tapered from height H6 to height H12at nose portion 246 a. Radius R12 can provide a smooth transitionbetween transition surfaces 246 b, 246 c and nose portion 246 a. HeightH12 is less than height H6 to facilitate insertion of leading endportion 246 into the spinal disc space.

In FIGS. 25A and 25B, distal portion 240 is provided with a body 242having upper and lower surfaces 242 a, 242 b curved along radius R7. Theupper and lower transition surfaces 246 b, 246 c of leading end portion246 can be tapered along angle A3 relative to central axis C extendinglongitudinally through body 242. Trial body 242 includes an overallmaximum height H7 between upper and lower surfaces 242 a, 242 b. Upperand lower surfaces 242 a, 242 b are tapered from height H7 to height H12at nose portion 246 a. Radius R12 can provide a smooth transitionbetween transition surfaces 246 b, 246 c and nose portion 246 a. HeightH12 is less than height H7 to facilitate insertion of leading endportion 246 into the spinal disc space.

In FIGS. 26A and 26B, distal portion 240 is provided with a body 242having upper and lower surfaces 242 a, 242 b curved along radius R8. Theupper and lower transition surfaces 246 b, 246 c of leading end portion246 can be tapered along angle A4 relative to central axis C extendinglongitudinally through body 242. Trial body 242 includes an overallmaximum height H8 between upper and lower surfaces 242 a, 242 b. Upperand lower surfaces 242 a, 242 b are tapered from height H8 to height H12at nose portion 246 a. Radius R12 can provide a smooth transitionbetween transition surfaces 246 b, 246 c and nose portion 246 a. HeightH12 is less than height H8 to facilitate insertion of leading endportion 246 into the spinal disc space. Upper and lower surfaces 242 a,242 b further taper along proximal end 248 to form angle α with thecentral axis of the insertion instrument to provide a smooth transitionbetween coupling portion 244 and body 242 to prevent body 242 fromhanging up or catching on the vertebral endplates as it is withdrawn.

In FIGS. 27A and 27B, distal portion 240 is provided with a body 242having upper and lower surfaces 242 a, 242 b curved along radius R9. Theupper and lower transition surfaces 246 b, 246 c of leading end portion246 can be tapered along angle A4 relative to central axis C extendinglongitudinally through body 242. Trial body 242 includes an overallmaximum height H9 between upper and lower surfaces 242 a, 242 b. Upperand lower surfaces 242 a, 242 b are tapered from height H9 to height H12at nose portion 246 a. Radius R12 can provide a smooth transitionbetween transition surfaces 246 b, 246 c and nose portion 246 a. HeightH12 is less than height H9 to facilitate insertion of leading endportion 246 into the spinal disc space. Upper and lower surfaces 242 a,242 b further taper along proximal end 248 to form angle α with thecentral axis of the insertion instrument to provide a smooth transitionbetween coupling portion 244 and body 242 to prevent body 242 fromhanging up or catching on the vertebral endplates as it is withdrawn.

In FIGS. 28A and 28B, distal portion 240 is provided with a body 242having upper and lower surfaces 242 a, 242 b curved along radius R10.The upper and lower transition surfaces 246 b, 246 c of leading endportion 246 can be tapered along angle A4 relative to central axis Cextending longitudinally through body 242. Trial body 242 includes anoverall maximum height H10 between upper and lower surfaces 242 a, 242b. Upper and lower surfaces 242 a, 242 b are tapered from height H10 toheight H12 at nose portion 246 a. Radius R12 can provide a smoothtransition between transition surfaces 246 b, 246 c and nose portion 246a. Height 1112 is less than height H10 to facilitate insertion ofleading end portion 246 into the spinal disc space. Upper and lowersurfaces 242 a, 242 b further taper along proximal end 248 to form angleα with the central axis of the insertion instrument.

In FIGS. 29A and 29B, distal portion 240 is provided with a body 242having upper and lower surfaces 242 a, 242 b curved along radius R11.The upper and lower transition surfaces 246 b, 246 c of leading endportion 246 can be tapered along angle A5 relative to central axis Cextending longitudinally through body 242. Trial body 242 includes anoverall maximum height H11 between upper and lower surfaces 242 a, 242b. Upper and lower surfaces 242 a, 242 b are tapered from height H11 toheight H12 at nose portion 246 a. Radius R12 can provide a smoothtransition between transition surfaces 246 b, 246 c and nose portion 246a. Height 1112 is less than height H11 to facilitate insertion ofleading end portion 246 into the spinal disc space. Upper and lowersurfaces 242 a, 242 b further taper along proximal end 248 to form angleα with the central axis of the insertion instrument.

It is contemplated that a set of self-distracting implants could beprovided by modifying each of the distal portions 240 of FIGS. 21A-29Bso that between its distal and proximal ends the implant has a lengththat fits within a spinal disc space. For example, shaft couplingportion 244 could be removed, or trial body 242 could be truncated at aproximal end wall 250. The proximal end of the implant could includes athreaded hole in the proximal end wall, notches in the lateral walls, orconfiguration for releasable engagement with an insertion instrument.

In one specific embodiment of a trial instrument set employing thedistal portions of FIGS.

21A-29B, each of the bodies 242 can be provided with a width W3 of about10 millimeters and a length L1 of about 42 millimeters. Each of thedistal portions 240 can be provided with an overall length L2 of about60 millimeters. Leading end portion 246 can be provided with a radius Rof 5 millimeters between lateral surfaces 242 c, 242 d.

In the specific embodiment, height H3 of the FIG. 21A embodiment is 7millimeters. Each of the heights H4 through H11 increase in onemillimeter increments from height H3 to height H11. Thus, height H11 is15 millimeters. Height H12 at nose portion 246 a is 3 millimeters foreach of the bodies 242. The radii R12 transitioning between nose portion246 a and upper and lower transition surfaces 246 b, 246 c can be about1.5 millimeters.

Transition surfaces 246 b, 246 c extend between radius R12 and theadjacent upper and lower surface 242 a, 242 b. The angular orientationof transition surfaces 246 b, 246 c relative to the central axis of thebody 242 can range from angle A1 to angle A5 for various ones of theembodiments shown. In one specific embodiment trial instrument set,angle A1 is about 15 degrees, angle A2 is about 20 degrees, angle A3 isabout 25 degrees, angle A4 is about 30 degrees, and angle A5 is about 35degrees. The specific embodiment further contemplates that upper andlower surface 242 a, 242 b can be provided with a different curvaturefor each of the bodies 242. For example, radius R3 can be about 179millimeters, radius R4 can be about 152 millimeters, radius R5 can beabout 133 millimeters, radius R6 can be about 119 millimeters, radius R7can be about 108 millimeters, radius R8 can be about 100 millimeters,radius R9 can be about 92 millimeters, radius R10 can be about 86millimeters, and radius R11 can be about 81 millimeters.

While specific dimensional and geometrical features have been providedfor one particular embodiment of a set of distal portions 240, it shouldbe understood however, that such dimensional and geometrical attributesare provided for a specific embodiment, and other embodimentscontemplate other dimensions than those provided herein.

The present invention contemplates various procedures and instrumentsets. For example, the surgeon can determine whether a trial body orimplant provides a desired disc space height by tactile feedback of theinserted trial body or implant, and also by visual inspection. Theinserted trial body or implant body should sufficiently stretch theremaining annulus tissue to provide firm engagement between the upperand lower surfaces of the trial or implant body and the adjacentvertebral endplates. Sufficient surface area contact should be presentto prevent or minimize post-operative movement of the adjacent vertebraerelative to the implant. By providing the trial bodies and implantbodies with correspondingly sized and shaped leading end portions, andby inserting the trial bodies and implant bodies in a non-distracteddisc space, the inserted trial or implant body provides immediatefeedback to the surgeon of the desirability of the fit. If distractionwere maintained by, for example, a second distractor, feedback to thesurgeon of the post-operative fit of the implant would not be reliableor available, if at all, until distraction were removed. As such, thetrial bodies and implants can be employed without utilization ofexternal distraction or distraction maintained in another disc spacelocation during trial body and implant insertion. However, secondarydistraction can be used to at least partially maintain disc spacedistraction upon withdrawal of the implants and trial bodies can beemployed. For example, pedicle screws and a rod can be employed on thecontralateral side to at least partially maintain distraction obtainedwith a particular implant or trial body.

Further, the trial bodies provide an indication of the fit of theimplant into the disc space location. Since the implant includes aleading end portion and height that corresponds to that of the trialbody, there is an immediate confirmation to the surgeon that thecorresponding implant will fit into the space occupied by the trialbody. If distraction were maintained at another location in the discspace or externally, there is no indication that the implant will fitproperly until the implant is inserted and distraction removed. As aresult, the implant may wedge too tightly in the disc space whendistraction is removed, making subsequent removal of the implantdifficult if an appropriate fit is not obtained. Alternatively, theimplant may be too loose when the distraction is removed due to overdistraction of the disc space.

The implants can be impacted or pushed into the disc space. As a result,disruption to the annulus tissue and tissue approaching the collapseddisc space is minimized since the lateral and vertical footprint of theimplant in the disc space can be the same as the lateral and verticalfootprint occupied in the implant's approach to the disc space. Also, byproviding the implant with the same footprint as the trial bodylaterally and vertically, and by performing distraction and implantinsertion through the same portal or pathway, no additional tissuedissection and/or retraction is required to accommodate distraction ofthe disc space during implant insertion.

The trial bodies and implants can be inserted into the disc space withminimal disc space preparation. According to one method, the collapseddisc space is accessed, and an opening is formed in the annulus having awidth corresponding to the width of the trial bodies and/or implants.Disc material is removed through the annulus opening, and, if desired bythe surgeon, manual roughening of the endplates is performed with ascraper or other suitable endplate roughening instrument. The trialbodies and/or implant bodies are then sequentially inserted and, ifnecessary, withdrawn through the annulus opening and into the discspace. Since the implants are self-distracting, it is not necessary tochisel, drill or otherwise form the vertebral endplates to receive theimplant, although such steps are not precluded. Consequently, fewersteps in the surgical procedure are necessary since requirements forbilateral distraction, external distraction, chiseling, drilling andreaming are eliminated. In addition, the lack of other instruments ordevices in the disc space facilitates visualization of the disc spacepreparation, trial body insertion, and/or implant insertion. Eliminationof cutting instruments in the disc space also theoretically improves thesafety of the procedure.

Minimally invasive techniques employing the trial instruments andimplants are contemplated. In any particular patient, the implants canbe inserted via any one or combination of posterior, postero-lateral,antero-lateral, transforaminal, far lateral and/or anterior approaches.Implant insertion can occur through a single pathway to a collapsedspinal disc space, or through multiple pathways to the collapsed discspace, or through multiple pathways to multiple levels of collapseddiscs of the spinal column. Since the implant, and trial instruments ifemployed, are inserted into the same disc space location from the sameapproach, the entire procedure for inserting an implant can be completedthrough one pathway. If a multiple pathway procedure is to be employed,the surgeon can complete implant insertion through one pathway beforecreating and moving to work in a second pathway.

Since distraction and implant insertion occur along the same pathway tothe collapsed disc space, the implants and trial instruments are suitedfor use in minimally invasive procedures which employ a retractor sleeveto provide a pathway to the collapsed disc space. Such retractor sleevescan employ any one or combination of an endoscopic viewing element inthe working channel, a microscopic viewing system over the proximal endof the retractor sleeve, fluoroscopic viewing, loupes, naked eye and/orimage guidance.

The trial bodies of the trial instruments and the implant bodies can bemade from any biocompatible material, including synthetic or naturalautograft, allograft or xenograft tissues, and can be resorbable ornon-resorbable in nature. Examples of tissue materials include hardtissues, connective tissues, demineralized bone matrix and combinationsthereof. Further examples of resorbable materials are polylactide,polyglycolide, tyrosine-derived polycarbonate, polyanhydride,polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite,bioactive glass, and combinations thereof. Further examples ofnon-resorbable materials are non-reinforced polymers, carbon-reinforcedpolymer composites, PEEK and PEEK composites, shape-memory alloys,titanium, titanium alloys, cobalt chrome alloys, stainless steel,ceramics and combinations thereof and others as well. If the trial bodyor implant is made from radiolucent material, radiographic markers canbe located on the trial body or implant to provide the ability tomonitor and determine radiographically or fluoroscopically the locationof the body in the spinal disc space. The material comprising the trialbodies can be solid, porous, spongy, perforated, drilled, and/or open.

There is contemplated an implant for insertion into a spinal disc spacebetween adjacent vertebrae. The implant can be impacted or pushed intothe disc space. The implant can be provided with a distal end or leadinginsertion end that is sized for insertion into the collapsed disc space.As the implant is inserted, the implant can restore the collapsed discspace to a desired disc space height. The desired disc space heightcorresponds to the height of the implant proximal the distal end. Onceinserted, the implant can maintain the disc space at the desired discspace height.

There is further contemplated an implant that, when inserted, restoresand maintains a desired disc space height of a collapsed disc spacebetween an upper vertebra and a lower vertebra. The implant includes abody with a distal end, a proximal end, an upper surface orientabletoward an endplate of the upper vertebra and a lower surface orientabletoward an endplate of the lower vertebra. The body of the implant has afirst height between the upper and lower surfaces corresponding to thedesired disc space height. The body of the implant also has a secondheight at its distal end that is less than a height of the collapseddisc space.

It is contemplated that the implants can be provided with bi-convexcurvature of the upper and lower surfaces, allowing the implants tocenter in the endplates of the disc space. It is further contemplatedthat the upper and lower surfaces of the implant can be planar orinclude compound geometry. The upper and lower surfaces of the implantcan also be configured to establish lordotic or kyphotic angulationbetween the adjacent vertebral bodies.

Also contemplated is a set of implants having two or more implants ofincreasing height. The height of each implant corresponds to a restoreddisc space height. The leading insertion end of each implant is sizedfor insertion into a collapsed disc space. As each implant is inserted,the implant restores the collapsed disc space to the restored disc spaceheight provided by the inserted implant. If the restored disc spaceheight does not correspond to the desired disc space height, theinserted implant is withdrawn and a larger height implant is inserted.Sequential insertion and withdrawal of increasing height implants iscontinued until the restored disc space height provided by an implant ofthe set of implants corresponds to the desired disc space height. Theimplant providing the desired disc space height is positioned in thedisc space to restore and post-operatively maintain the desired discspace height.

There is further contemplated an instrument set having two or moreself-distracting trial instruments and at least one implant. The two ormore trial instruments each have a body with a leading insertion endsized for insertion into a collapsed disc space. The leading insertionends of each trial body are substantially the same in size and shape.Each trial body has a height proximal the leading insertion end thatrestores the collapsed disc space height to a height different than thatof the other trial bodies. The at least one implant has a leadinginsertion end that is substantially the same in size and shape as theleading insertion end of at least one of the trial bodies of the trialinstruments. The implant has a height proximal its leading insertion endthat corresponds to the desired restored disc space height provided bythe at least one trial body.

Also contemplated is a kit including a set of trial instruments, eachhaving a trial body at a distal end thereof. The trial bodies have aself-distracting leading end portion insertable in a collapsed spinaldisc space. The kit further includes a set of implants positionable inthe collapsed spinal disc space. Each implant has a body sized andshaped to correspond in size and shape to a respective trial body of thetrial instruments. The fit of each implant body in the spinal disc spaceis indicated to the surgeon by the fit of the corresponding trial bodyof the trial instruments. When a trial body provides a desired fit, thetrial body is removed and the implant corresponding to the trial body isinserted into the collapsed disc space in the location previouslyoccupied by the withdrawn trial body.

It is contemplated that an insertion instrument can be engaged tolateral walls of an intervertebral implant. The insertion instrumentincludes a distal coupling portion positionable in notches formed incorresponding ones of the lateral walls of the implant. The couplingportion has a first position engaging the implant in the notches and asecond position disengaged from the implant in the notches. The width ofthe coupling portion in each of its first and second positions is lessthan the width of the implant between the lateral walls of the implant.

Methods for inserting an intervertebral implant into a collapsed spinaldisc space are also contemplated. A number of implants are sequentiallyinserted into the collapsed disc space to restore the disc space. If aparticular implant does not restore the disc space to a desired discspace height, the implant is withdrawn from the disc space. When aninserted implant is withdrawn, the disc space is non-distracted andallowed to collapse. The implant providing the desired disc space heightremains in the disc space to post-operatively maintain the desired discspace height.

A method is contemplated for inserting an intervertebral implant thatincludes accessing a collapsed spinal disc space from an uni-portalapproach. A first implant is inserted through the portal into the discspace to restore the disc space height. If the restored disc spaceheight does not correspond to a desired disc space height, the insertedimplant is removed from the disc space and portal, and the disc space isallowed to collapse. A second implant of different height is insertedinto the undistracted, collapsed disc space to provide another restoreddisc space height. When an inserted implant provides a restored discspace height that corresponds to a desired disc space height, theinserted implant remains in the disc space to post-operatively maintainthe desired disc space height.

Also contemplated is a method for inserting an intervertebral implant isprovided that includes accessing a collapsed spinal disc space. A numberof trial bodies are provided with leading end portions sized forinsertion into a non-distracted disc space. The trial bodies aresequentially inserted into and removed from the disc space. The trialbody providing the desired disc space height is used to select animplant having a height and a self-distracting leading end portioncorresponding to the height and leading end portion of the last insertedtrial body. The implant is then inserted into the non-distracted discspace to restore the disc space and post-operatively maintain thedesired disc space height.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, and that all changes andmodifications that come within the spirit of the invention are desiredto be protected.

I claim:
 1. A spinal implant for insertion between an upper vertebralbody and a lower vertebral body, the spinal implant comprising: atrailing end surface, a leading end portion terminating in a noseportion having a terminal end surface, a length between the trailing endsurface and the terminal end surface, a mid-longitudinal axis extendingalong the length through the trailing end surface and the terminal endsurface of the nose portion, an upper surface extending from adjacentthe trailing end surface to the leading end portion, the upper surfacebeing orientable toward an end plate of the upper vertebral body whenthe spinal implant is inserted between the upper and lower vertebralbodies, and a lower surface extending from adjacent the trailing endsurface to the leading end portion, the lower surface being orientabletoward an end plate of the lower vertebral body when the spinal implantis inserted between the upper and lower vertebral bodies, wherein afirst plane extends through the trailing end surface, the leading endportion, the upper surface, the lower surface, and the mid-longitudinalaxis, and along the length, the nose portion being substantially arcuatein the first plane, wherein the leading end portion extends from asecond plane to the terminal end surface, the second plane beingperpendicular to the mid-longitudinal axis and the first plane,extending through the upper surface and the lower surface, and beingdisposed between the trailing end surface and the terminal end surface,wherein the leading end portion includes a first surface extending fromthe upper surface to the nose portion, and a second surface extendingfrom the lower surface to the nose portion, and wherein the terminal endsurface extends between a third plane and a fourth plane, the thirdplane and the fourth plane being parallel to the mid-longitudinal axisand perpendicular to the first plane and the second plane, the distancebetween the third plane and the fourth plane at the intersection withthe second plane being less than a third of a distance between the uppersurface and the lower surface in the second plane.
 2. The spinal implantof claim 1, wherein the nose portion is substantially semi-circular inthe first plane.
 3. The spinal implant of claim 2, wherein the firstsurface provides a smooth and gradual transition from the upper surfaceto the terminal end surface, and the second surface provides a smoothand gradual transition from the lower surface to the terminal endsurface.
 4. The spinal implant of claim 3, wherein a distance betweenthe trailing end surface and the second plane is approximatelytwo-thirds of the length of the spinal implant.
 5. The spinal implant ofclaim 1, wherein a fifth plane perpendicular to the mid-longitudinalaxis intersects the mid-longitudinal axis halfway between the secondplane and the terminal end surface, a sixth plane perpendicular to themid-longitudinal axis intersects the mid-longitudinal axis halfwaybetween the second plane and the fifth plane, a seventh planeperpendicular to the mid-longitudinal axis intersects themid-longitudinal axis halfway between the fifth plane and the terminalend surface, a distance between the first surface and the second surfacein the second plane being greater than a distance between the firstsurface and the second surface in the sixth plane, a distance betweenthe first surface and the second surface in the sixth plane beinggreater than a distance between the first surface and the second surfacein the fifth plane, and a distance between the first surface and thesecond surface in the fifth plane being greater than a distance betweenthe first surface and the second surface in the seventh plane.
 6. Thespinal implant of claim 1, wherein a fifth plane perpendicular to themid-longitudinal axis extends through the upper surface, the lowersurface, and the midpoint between the trailing end surface and theterminal end surface, and a trailing end portion of the spinal implantextends from a sixth plane to the trailing end surface, the sixth planebeing perpendicular to the mid-longitudinal axis and extending throughthe upper surface and the lower surface, a distance between the uppersurface and the lower surface in the fifth plane being substantiallyequal to a distance between the upper surface and the lower surface inthe sixth plane.
 7. The spinal implant of claim 6, wherein a seventhplane perpendicular to the first plane and the second plane extendsthrough the mid-longitudinal axis and along the length, the seventhplane intersecting the terminal end surface and the sixth plane, aneighth plane perpendicular to the first plane and the second planeextends parallel to the seventh plane along the upper surface, theeighth plane intersecting the sixth plane, a ninth plane perpendicularto the first plane and the second plane extends parallel to the seventhplane along the lower surface, the eighth plane intersecting the sixthplane, a tenth plane perpendicular to the first plane and the secondplane extends parallel to the seventh plane and eighth plane halfwaytherebetween, the tenth plane intersecting the sixth plane and the firstsurface, an eleventh plane perpendicular to the first plane and thesecond plane extends parallel to the seventh plane and the ninth planehalfway therebetween, the eleventh plane intersecting the sixth planeand the second surface, a distance between the first surface and thesixth plane in the tenth plane being less than a distance between theterminal end surface and the sixth plane in the seventh plane, and adistance between the second surface and the sixth plane in the eleventhplane being less than the distance between the terminal end surface andthe sixth plane in the seventh plane.
 8. The spinal implant of claim 7,wherein a distance between the trailing end surface and the second planeis approximately two-thirds of the length of the spinal implant, and atleast one of the upper surface and the lower surface is roughened. 9.The spinal implant of claim 1, wherein a first curved surfacetransitions the upper surface to the trailing end surface, and a secondcurved surface transitions the lower surface to the trailing endsurface, the radii of curvature of the first curved surface and thesecond curved surface in the first plane being greater than the radiusof curvature of the terminal end surface in the first plane.
 10. Thespinal implant of claim 9, wherein a distance between the trailing endsurface and the second plane is approximately two-thirds of the lengthof the spinal implant, and at least one of the upper surface and thelower surface is roughened.
 11. A spinal implant for insertion betweenan upper vertebral body and a lower vertebral body, the spinal implantcomprising: a leading end portion terminating in a nose portion having aterminal end surface, a mid-longitudinal axis extending through theterminal end surface of the nose portion, an upper surface beingorientable toward an end plate of the upper vertebral body when thespinal implant is inserted between the upper and lower vertebral bodies,and a lower surface being orientable toward an end plate of the lowervertebral body when the spinal implant is inserted between the upper andlower vertebral bodies, wherein a first plane extends through theleading end portion, the upper surface, and the lower surface, and alongthe mid-longitudinal axis, the nose portion being substantiallysemi-circular in the first plane, wherein the leading end portionextends from a second plane to the terminal end surface, the secondplane being perpendicular to the mid-longitudinal axis and the firstplane, extending through the upper surface and the lower surface,wherein the leading end portion includes a first surface extending fromthe upper surface to the nose portion, and a second surface extendingfrom the lower surface to the nose portion, and wherein the terminal endsurface extends between a third plane and a fourth plane, the thirdplane and the fourth plane being parallel to the mid-longitudinal axisand perpendicular to the first plane and the second plane, the distancebetween the third plane and the fourth plane at the intersection withthe second plane being less than a third of a distance between the uppersurface and the lower surface in the second plane.
 12. The spinalimplant of claim 11, wherein the first surface provides a smooth andgradual transition from the upper surface to the terminal end surface,and the second surface provides a smooth and gradual transition from thelower surface to the terminal end surface.
 13. The spinal implant ofclaim 11, wherein a fifth plane perpendicular to the mid-longitudinalaxis intersects the mid-longitudinal axis halfway between the secondplane and the terminal end surface, a sixth plane perpendicular to themid-longitudinal axis intersects the mid-longitudinal axis halfwaybetween the second plane and the fifth plane, a seventh planeperpendicular to the mid-longitudinal axis intersects themid-longitudinal axis halfway between the fifth plane and the terminalend surface, a distance between the first surface and the second surfacein the second plane being greater than a distance between the firstsurface and the second surface in the sixth plane, a distance betweenthe first surface and the second surface in the sixth plane beinggreater than a distance between the first surface and the second surfacein the fifth plane, and a distance between the first surface and thesecond surface in the fifth plane being greater than a distance betweenthe first surface and the second surface in the seventh plane.
 14. Thespinal implant of claim 11, wherein a fifth plane perpendicular to themid-longitudinal axis extends through the upper surface, the lowersurface, and the midpoint between a trailing end surface of the spinalimplant and the terminal end surface, and a trailing end portion of thespinal implant extends from a sixth plane to the trailing end surface,the sixth plane being perpendicular to the mid-longitudinal axis andextending through the upper surface and the lower surface, a distancebetween the upper surface and the lower surface in the fifth plane beingsubstantially equal to a distance between the upper surface and thelower surface in the sixth plane.
 15. The spinal implant of claim 14,wherein a seventh plane perpendicular to the first plane and the secondplane extends along the mid-longitudinal axis, the seventh planeintersecting the terminal end surface and the sixth plane, an eighthplane perpendicular to the first plane and the second plane extendsparallel to the seventh plane along at least a portion of the uppersurface, the eighth plane intersecting the sixth plane, a ninth planeperpendicular to the first plane and the second plane extends parallelto the seventh plane along at least a portion of the lower surface, theeighth plane intersecting the sixth plane, a tenth plane perpendicularto the first plane and the second plane extends parallel to the seventhplane and eighth plane halfway therebetween, the tenth planeintersecting the sixth plane and the first surface, an eleventh planeperpendicular to the first plane and the second plane extends parallelto the seventh plane and the ninth plane halfway therebetween, theeleventh plane intersecting the sixth plane and the second surface, adistance between the first surface and the sixth plane in the tenthplane being less than a distance between the terminal end surface andthe sixth plane in the seventh plane, and a distance between the secondsurface and the sixth plane in the eleventh plane being less than thedistance between the terminal end surface and the sixth plane in theseventh plane.
 16. A spinal implant for insertion between an uppervertebral body and a lower vertebral body, the spinal implantcomprising: a proximal end and an opposite distal end; a trailing endportion extending from the proximal end toward the distal end; a leadingend portion extending from the distal end toward the proximal end, theleading end portion including a nose portion terminating at a terminalend surface provided at and adjacent the distal end, a mid-longitudinalaxis extending through the terminal end surface of the nose portion, andan upper surface and a lower surface each having portions opposite fromone another, wherein a first plane extends through the leading endportion, the upper surface, and the lower surface, and along themid-longitudinal axis, the terminal end surface being substantiallysemi-circular in the first plane, wherein the leading end portionextends from a second plane to the terminal end surface, the secondplane being perpendicular to the mid-longitudinal axis and the firstplane, extending through the upper surface and the lower surface,wherein the leading end portion includes a first surface extending fromthe upper surface to the nose portion, and a second surface extendingfrom the lower surface to the nose portion, and wherein the terminal endsurface extends between a third plane and a fourth plane, the thirdplane and the fourth plane being parallel to the mid-longitudinal axisand perpendicular to the first plane and the second plane, the distancebetween the third plane and the fourth plane at the intersection withthe second plane being less than a third of a distance between the uppersurface and the lower surface in the second plane.
 17. The spinalimplant of claim 16, wherein the first surface provides a smooth andgradual transition from the upper surface to the terminal end surface,and the second surface provides a smooth and gradual transition from thelower surface to the terminal end surface.
 18. The spinal implant ofclaim 16, wherein a fifth plane perpendicular to the mid-longitudinalaxis intersects the mid-longitudinal axis halfway between the secondplane and the terminal end surface, a sixth plane perpendicular to themid-longitudinal axis intersects the mid-longitudinal axis halfwaybetween the second plane and the fifth plane, a seventh planeperpendicular to the mid-longitudinal axis intersects themid-longitudinal axis halfway between the fifth plane and the terminalend surface, a distance between the first surface and the second surfacein the second plane being greater than a distance between the firstsurface and the second surface in the sixth plane, a distance betweenthe first surface and the second surface in the sixth plane beinggreater than a distance between the first surface and the second surfacein the fifth plane, and a distance between the first surface and thesecond surface in the fifth plane being greater than a distance betweenthe first surface and the second surface in the seventh plane.
 19. Thespinal implant of claim 16, wherein a fifth plane perpendicular to themid-longitudinal axis extends through the upper surface, the lowersurface, and the midpoint between a trailing end surface of the spinalimplant and the terminal end surface, and a trailing end portion of thespinal implant extends from a sixth plane to the trailing end surface,the sixth plane being perpendicular to the mid-longitudinal axis andextending through the upper surface and the lower surface, a distancebetween the upper surface and the lower surface in the fifth plane beingsubstantially equal to a distance between the upper surface and thelower surface in the sixth plane.
 20. The spinal implant of claim 19,wherein a seventh plane perpendicular to the first plane and the secondplane extends along the mid-longitudinal axis, the seventh planeintersecting the terminal end surface and the sixth plane, an eighthplane perpendicular to the first plane and the second plane extendsparallel to the seventh plane along at least a portion of the uppersurface, the eighth plane intersecting the sixth plane, a ninth planeperpendicular to the first plane and the second plane extends parallelto the seventh plane along at least a portion of the lower surface, theeighth plane intersecting the sixth plane, a tenth plane perpendicularto the first plane and the second plane extends parallel to the seventhplane and eighth plane halfway therebetween, the tenth planeintersecting the sixth plane and the first surface, an eleventh planeperpendicular to the first plane and the second plane extends parallelto the seventh plane and the ninth plane halfway therebetween, theeleventh plane intersecting the sixth plane and the second surface, adistance between the first surface and the sixth plane in the tenthplane being less than a distance between the terminal end surface andthe sixth plane in the seventh plane, and a distance between the secondsurface and the sixth plane in the eleventh plane being less than thedistance between the terminal end surface and the sixth plane in theseventh plane.